Good point, the heat inside of a case can build quickly and then transfer than heat over to the CPU within an hour or two.  

I know there are those who will disagree, but I used to build cased for the big companies, IBM, etc.  We found that if we had a good intake and exhaust fan, sometimes it made no difference, because the power supply was the major heat source.  By just opening the case or in extreme conditions adding gently air flow, the heating stopped.  

I say gentle air flow, becasue if you add too much airflow you will reduce the intake effeicency of the CPU fan and it will fail to cool and casue more overheating. 

Personally, I think your mobo and video card are history and it is time to build new.  Sorry that is not much help.

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